U.S. patent application number 15/080799 was filed with the patent office on 2016-09-29 for damping air spring and shock absorber combination for heavy-duty vehicle axle/suspension systems.
The applicant listed for this patent is HENDRICKSON USA, L.L.C.. Invention is credited to R. Scott Fulton, Thomas J. Long, Andrew J. Westnedge.
Application Number | 20160280033 15/080799 |
Document ID | / |
Family ID | 55858881 |
Filed Date | 2016-09-29 |
United States Patent
Application |
20160280033 |
Kind Code |
A1 |
Fulton; R. Scott ; et
al. |
September 29, 2016 |
DAMPING AIR SPRING AND SHOCK ABSORBER COMBINATION FOR HEAVY-DUTY
VEHICLE AXLE/SUSPENSION SYSTEMS
Abstract
A damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems includes a damping air
spring and a shock absorber both operatively attached to the
axle/suspension system. The damping air spring primarily provides
damping to the axle/suspension system over a first range of
frequencies. The shock absorber primarily provides damping to the
axle/suspension system over a second range of frequencies. The
first range of frequencies is from about 0.0 Hz to about 6.0 Hz and
the second range of frequencies is from about 0.0 Hz to about 13.0
Hz.
Inventors: |
Fulton; R. Scott; (Hudson,
OH) ; Westnedge; Andrew J.; (Granville, OH) ;
Long; Thomas J.; (Canton, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HENDRICKSON USA, L.L.C. |
Itasca |
IL |
US |
|
|
Family ID: |
55858881 |
Appl. No.: |
15/080799 |
Filed: |
March 25, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62137866 |
Mar 25, 2015 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60G 2300/026 20130101;
B60G 11/27 20130101; B60G 17/08 20130101; B60G 9/003 20130101; B60G
2500/10 20130101; F16F 9/05 20130101; B60G 2202/30 20130101; B60G
2300/02 20130101; B60G 15/12 20130101; B60G 2202/242 20130101; F16F
15/022 20130101; B60G 2202/152 20130101; B60G 2500/114
20130101 |
International
Class: |
B60G 15/12 20060101
B60G015/12; B60G 9/00 20060101 B60G009/00; B60G 17/08 20060101
B60G017/08 |
Claims
1. A damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems comprising: a damping
air spring operatively attached to said axle/suspension system, and
a shock absorber operatively attached to said axle/suspension
system, whereby said damping air spring primarily provides damping
to the axle/suspension system over a first critical range of
frequencies and said shock absorber primarily provides damping to
the axle/suspension system over a second range of critical
frequencies, said first range of critical frequencies and said
second range of critical frequencies being different from one
another.
2. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 1, wherein said
first critical range of frequencies is from about 0.0 Hz to about
6.0 Hz.
3. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 1, wherein said
second range of critical frequencies is from about 0.0 Hz to about
13 Hz
4. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 1, wherein said
second range of critical frequencies is greater than about 6.0
Hz.
4. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 1, said damping
air spring further comprising a bellows chamber and a piston
chamber, said bellows chamber being in fluid communication with
said piston chamber via at least one opening.
5. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 4, said piston
chamber comprising an external reservoir located outside of said
air spring.
6. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 4, said piston
chamber being located within a piston of said air spring.
7. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 4, said at
least one opening having a cross-sectional area of from about 0.039
in..sup.2 to about 0.13 in..sup.2.
8. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 7, wherein the
ratio of a cross-sectional area of said at least one opening
measured in in..sup.2 to the volume of said piston chamber measured
in in..sup.3 to a volume of said bellows chamber measured in
in..sup.3 is in the range of ratios of from about 1:600:1200 to
about 1:14100:23500.
9. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 4, said piston
chamber having a volume of from about 150 in..sup.3 to about 550
in..sup.3.
10. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 4, said bellows
chamber having a volume of from about 305 in..sup.3 to about 915
in..sup.3.
11. The damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems of claim 1, said shock
absorber including a blow off valve that generates reduced damping
across all frequencies.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 62/137,866, filed Mar. 25, 2015.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to the art of
axle/suspension systems for heavy-duty vehicles. More particularly,
the invention relates to air-ride axle/suspension systems for
heavy-duty vehicles which utilize a damping air spring to cushion
the ride of the vehicle. More specifically, the invention is
directed to the combination of a damping air spring utilized in
conjunction with a shock absorber for heavy-duty vehicle air-ride
axle/suspension systems, in which the damping air spring is
optimized to aid in providing damping characteristics to the
axle/suspension system at a selected frequency range, and the shock
absorber is optimized to aid in providing damping to the
axle/suspension system at a selected frequency range generally
different from the frequency range damped by the damping air
spring. The combination of the damping air spring and shock
absorber working together supplement one another to provide
optimized damping across the entire range of critical frequencies
encountered by the axle/suspension system during operation, thereby
increasing the soft ride characteristics of the axle/suspension
system and extending the life of the components of the
axle/suspension system, tires and other vehicle components, as well
as potentially reducing weight of the axle/suspension system.
[0004] 2. Background Art
[0005] The use of one or more air-ride trailing and leading arm
rigid beam-type axle/suspension systems has been very popular in
the heavy-duty truck, bus and tractor-trailer industry for many
years. Although such axle/suspension systems can be found in widely
varying structural forms, in general their structure is similar in
that each system typically includes a pair of suspension
assemblies. In some heavy-duty vehicles, the suspension assemblies
are connected directly to the primary frame of the vehicle. In
other heavy-duty vehicles, the primary frame of the vehicle
supports a subframe, and the suspension assemblies connect directly
to the subframe. For those heavy-duty vehicles that support a
subframe, the subframe can be non-movable or movable, the latter
being commonly referred to as a slider box, slider subframe, slider
undercarriage, or secondary slider frame. For the purpose of
convenience and clarity, reference herein will be made to main
members, with the understanding that such reference is by way of
example, and that the present invention applies to heavy-duty
vehicle axle/suspension systems suspended from main members of:
primary frames, movable subframes and non-movable subframes.
[0006] Specifically, each suspension assembly of an axle/suspension
system includes a longitudinally extending elongated beam. Each
beam typically is located adjacent to and below a respective one of
a pair of spaced-apart longitudinally extending main members and
one or more cross members which form the frame of the vehicle. More
specifically, each beam is pivotally connected at one of its ends
to a hanger, which in turn is attached to and depends from a
respective one of the main members of the vehicle. An axle extends
transversely between and typically is connected by some means to
the beams of the pair of suspension assemblies at a selected
location from about the mid-point of each beam to the end of the
beam opposite from its pivotal connection end. The beam end
opposite the pivotal connection end also is connected to an air
spring, or its equivalent, which in turn is connected to a
respective one of the main members. The air springs cushion the
ride of the vehicle during operation, and in some cases, provide
damping. A height control valve is mounted on the main member or
other support structure and is operatively connected to the beam
and to the air spring in order to maintain the ride height of the
vehicle. A brake system and one or more shock absorbers also are
mounted on the axle/suspension system. The shock absorbers provide
damping to the axle/suspension system of the vehicle during
operation. The beam may extend rearwardly or frontwardly from the
pivotal connection relative to the front of the vehicle, thus
defining what are typically referred to as trailing arm or leading
arm axle/suspension systems, respectively. However, for purposes of
the description contained herein, it is understood that the term
"trailing arm" will encompass beams which extend either rearwardly
or frontwardly with respect to the front end of the vehicle.
[0007] The axle/suspension systems of the heavy-duty vehicle act to
cushion the ride, dampen vibrations and stabilize the vehicle. More
particularly, as the vehicle is traveling over the road, its wheels
encounter road conditions that impart various forces, loads, and/or
stresses, collectively referred to herein as forces, to the
respective axle on which the wheels are mounted, and in turn, to
the suspension assemblies that are connected to and support the
axle. In order to minimize the detrimental effect of these forces
on the vehicle as it is operating, the axle/suspension system is
designed to react and/or absorb at least some of the forces.
[0008] These forces include vertical forces caused by vertical
movement of the wheels as they encounter certain road conditions,
fore-aft forces caused by acceleration and deceleration of the
vehicle, and side-load and torsional forces associated with
transverse vehicle movement, such as turning of the vehicle and
lane-change maneuvers. In order to address such disparate forces,
axle/suspension systems have differing structural requirements.
More particularly, it is desirable for an axle/suspension system to
be fairly stiff in order to minimize the amount of sway experienced
by the vehicle and thus provide what is known in the art as roll
stability. However, it is also desirable for an axle/suspension
system to be relatively flexible to assist in cushioning the
vehicle from vertical impacts, and to provide compliance so that
the components of the axle/suspension system resist failure,
thereby increasing durability of the axle/suspension system. It is
also desirable to dampen the vibrations or oscillations that result
from such forces.
[0009] A key component of the axle/suspension system that cushions
the ride of the vehicle from vertical impacts is the air spring,
while a shock absorber typically provides damping characteristics
to the axle/suspension system, although air springs with damping
features have also been utilized.
[0010] The typical air spring without damping features of the type
utilized in heavy-duty air-ride axle/suspension systems includes
three main components: a flexible bellows, a piston and a bellows
top plate. The bellows is typically formed from rubber or other
flexible material, and is operatively mounted on top of the piston.
The piston is typically formed from steel, aluminum, fiber
reinforced plastic or other rigid material and is mounted on the
rear end of the top plate of the beam of the suspension assembly by
fasteners, which are generally well known in the art. The volume of
pressurized air, or "air volume", that is contained within the air
spring is a major factor in determining the spring rate of the air
spring. More specifically, this air volume is contained within the
bellows and, in some cases, the piston of the air spring. The
larger the air volume of the air spring, the lower the spring rate
of the air spring. A lower spring rate is generally more desirable
in the heavy-duty vehicle industry because it provides a softer
ride to the vehicle during operation. Typically, the piston either
contains a hollow cavity, which is in communication with the
bellows and which adds to the air volume of the air spring by
allowing unrestricted communication of air between the piston and
the bellows volumes, or the piston has a generally hollow
cylindrical-shape and does not communicate with the bellows volume,
whereby the piston does not contribute to the air volume of the air
spring. The air volume of the air spring is in fluid communication
with an air source, such as an air supply tank, and also is in
fluid communication with the height control valve of the vehicle.
The height control valve, by directing air flow into and out of the
air spring of the axle/suspension system, helps maintain the
desired ride height of the vehicle.
[0011] Prior art air springs such as the one described above, while
providing cushioning to the vehicle, cargo and occupant(s) during
operation of the vehicle, provide little, if any, damping to the
axle/suspension system. Such damping is instead typically provided
by a pair of hydraulic shock absorbers, although a single shock
absorber has also been utilized and is generally well known in the
art. The shock absorber typically includes a cylinder that is
filled with fluid. A plunger with a diaphragm mounted on its end is
disposed longitudinally within the fluid filled cylinder so that
the plunger and diaphragm can move within the fluid filled
cylinder. The diaphragm typically includes a number of openings and
also includes a blow off valve that is mounted on the diaphragm.
The blow off valve includes larger openings that allow a two-stage
damping curve that is generally well known in the art. The shock
absorber cylinder is mounted to the beam of a respective one of the
suspension assemblies and the plunger is mounted to a respective
one of the main members of the vehicle. As the beam is rotated
upwardly toward the main member during operation of the vehicle,
the plunger and diaphragm are moved downwardly through the fluid
filled cylinder. As the beam is rotated downwardly away from the
main member during operation of the vehicle, the plunger and
diaphragm are moved upwardly through the fluid filled cylinder. The
movement of the plunger and diaphragm through the fluid filled
cylinder results in viscous damping of the axle/suspension
system.
[0012] For trailers of heavy-duty vehicles, the frequencies where
optimal damping of the axle/suspension system(s) is critical are
from about 1.8 Hz, body bounce mode, to about 13 Hz, wheel hop
mode. At these natural frequencies, the axle/suspension system is
predisposed to move, so road inputs at these frequencies can result
in a build-up of movement in the axle/suspension system that can
potentially adversely affect the performance of the axle/suspension
system.
[0013] Prior art shock absorbers have a continuously increasing
damping curve at higher frequencies. This means that as the
frequency of the inputs on the axle/suspension system increase, the
damping provided by the shock absorber to the axle/suspension
system is increased. This increased damping at higher input
frequencies causes increased transmissibility of the forces acting
on the axle/suspension system through the shock absorbers, which in
turn can reduce the soft ride characteristics of the
axle/suspension system at higher frequencies and can also lead to
premature wear of the components of the axle/suspension system,
tires and other vehicle components. The continuously increasing
damping curve of the prior art shock absorbers can also potentially
cause "misting" of the shock absorber. More specifically, misting
occurs when fluid contained in the shock absorber is forced out
around the plunger of the shock absorber during operation of the
shock absorber. This occurs when high energy road inputs are
imparted to the axle/suspension system through the wheels of the
vehicle during operation of the vehicle. These high energy inputs
on the axle/suspension system cause a larger damping force in the
prior art shock absorber because of the continuously increasing
damping curve of shock absorbers. This increased damping force in
turn causes the shock absorber to generate very high internal
pressures, which can cause the shock absorber to mist. Although
misting of the shock absorber does not typically compromise the
ability of the shock absorber to provide damping, misting can
adversely affect components surrounding the shock absorber by
contaminating them with fluid from the shock absorber and also may
result in the belief that the shocks or other components have
failed, when they have not, resulting in premature replacement of
the shocks or other components which adds additional costs.
Therefore, reducing the amount of misting of the shock absorber is
preferred in order to minimize the possibility of contamination of
surrounding components and premature replacement of the shocks or
other vehicle components. In addition, the increased damping force
of the prior art shock absorber at higher frequencies can cause
increased stress to the components of the axle/suspension system
that can in turn potentially increase wear and reduce the life of
the components of the axle/suspension system, tires and other
vehicle components.
[0014] The amount of cargo that a vehicle may carry is governed by
local, state, and/or national road and bridge laws. The basic
principle behind most road and bridge laws is to limit the maximum
load that a vehicle may carry, as well as to limit the maximum load
that can be supported by individual axles. Because standard prior
art shock absorbers are relatively heavy, these components add
undesirable weight to the axle/suspension system and therefore
reduce the amount of cargo that can be carried by the heavy-duty
vehicle. Depending on the shock absorbers employed, they also add
varying degrees of complexity to the axle/suspension system, which
is also undesirable.
[0015] Air springs with damping features, such as the one described
in U.S. Pat. No. 8,540,222 owned by the assignee of the present
application, are also known. The air spring with damping features
shown and described in the '222 patent can be incorporated into
axle/suspension systems, such as the one described above, and
includes a bellows and a piston. The top end of the bellows is
sealingly engaged with a bellows top plate. An air spring mounting
plate is mounted on the top portion of the top plate by fasteners,
which are also used to mount the top portion of the air spring to a
respective one of the main members of the vehicle. The piston is
generally cylindrical-shaped and includes a continuous generally
stepped sidewall attached to a generally flat bottom plate and
integrally formed with a top plate. The piston bottom plate is
formed with a central opening. A fastener is disposed through the
opening in order to attach the piston to the beam top plate at the
rear end of the beam.
[0016] The top plate, sidewall and bottom plate of the piston
define a piston chamber having an interior volume. The piston top
plate is formed with a circular upwardly extending protrusion
having a lip around its circumference. The lip cooperates with the
lowermost end of the bellows to form an airtight seal between the
bellows and the lip. Alternate means of attachment are also known
and are commonly used in the art. The bellows, top plate and piston
top plate define a bellows chamber having an interior volume. The
piston top plate is formed with a pair of openings, which allow the
volume of the piston chamber and the volume of the bellows chamber
to communicate with one another. The piston chamber volume, the
bellows chamber volume and the cross-sectional area of the openings
formed in the piston top plate between the piston chamber and the
bellows chamber provide damping characteristics to the air spring
during operation of the vehicle.
[0017] Other prior art air springs have attempted to provide
damping characteristics to the air spring by placing valves between
the bellows and piston chambers of the air spring. Still other
prior art air springs have attempted to provide damping
characteristics to the air spring by forming an opening between the
bellows and piston chambers of the air spring which is partially
covered by rubber flaps mounted adjacent to the opening.
[0018] These prior art air springs with damping features may
potentially provide less than optimal damping at higher frequencies
above about 5 Hz, which can in turn potentially cause reduced life
of the components of the axle/suspension system, including
potentially increased tire wear and payload damage.
[0019] The combination damping air spring and shock absorber of the
present invention overcomes the problems associated with prior art
damping air springs and shock absorbers utilized with non-damping
air springs, by providing an optimized damping air spring that is
utilized in combination with an optimized shock absorber resulting
in improved damping characteristics for the axle/suspension system
across the entire spectrum of critical input frequencies. The
combination damping air spring and shock absorber for heavy-duty
vehicles allows tuning of certain structural components of the
shock absorber to provide optimal damping at higher frequencies,
resulting in improved damping to the axle/suspension system while
reducing transmissibility of forces and misting that are common in
prior art standard shock absorbers, saving weight and cost, and
enabling the heavy-duty vehicle to haul more cargo. Moreover,
reducing transmissibility of road inputs into the components of the
axle/suspension system during operation of the vehicle increases
the durability of the axle/suspension system and the components of
the axle/suspension system, while maintaining the soft ride
characteristics of the axle/suspension system at higher critical
input frequencies. In addition, the damping air spring provides
optimal damping at lower frequencies below about 5 Hz, which in
turn increases the life of components of the axle/suspension
system, tires and other vehicle components.
SUMMARY OF THE INVENTION
[0020] Objectives of the present invention include providing a
damping air spring and shock absorber combination for heavy-duty
vehicle axle/suspension systems that optimizes damping across the
entire range of critical frequencies encountered by the
axle/suspension system during operation.
[0021] A further objective of the present invention is to provide a
damping air spring and shock absorber combination for heavy-duty
vehicle axle/suspension systems that allows tuning of certain
structural components of the shock absorber to provide optimal
damping at higher frequencies, resulting in improved damping to the
axle/suspension system while reducing transmissibility of forces
and misting that are common in prior art standard shock
absorbers.
[0022] Yet another objective of the present invention is to provide
a damping air spring and shock absorber combination for heavy-duty
vehicle axle/suspension systems that reduces weight and costs, and
enables the heavy-duty vehicle to haul more cargo.
[0023] Still another objective of the present invention is to
provide a damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems that reduces
transmissibility of road inputs into the components of the
axle/suspension system during operation of the vehicle, which
increases the durability of the axle/suspension system and the
components of the axle/suspension system while maintaining the soft
ride characteristics of the axle/suspension system at higher
critical input frequencies.
[0024] An even further objective of the present invention is to
provide a damping air spring and shock absorber combination for
heavy-duty vehicle axle/suspension systems whereby the damping air
spring provides optimal damping at lower frequencies, below about 5
Hz, which in turn increases the life of components of the
axle/suspension system, tires and other vehicle components.
[0025] These objectives and advantages are obtained by the damping
air spring and shock absorber combination for heavy-duty vehicle
axle/suspension systems of the present invention which includes a
damping air spring operatively attached to the axle/suspension
system, and a shock absorber operatively attached to the
axle/suspension system. The damping air spring primarily provides
damping to the axle/suspension system over a first critical range
of frequencies and the shock absorber primarily provides damping to
the axle/suspension system over a second range of critical
frequencies. The first range of critical frequencies and the second
range of critical frequencies are different from one another.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0026] The preferred embodiment of the present invention,
illustrative of the best mode in which applicant has contemplated
applying the principles, is set forth in the following description
and is shown in the drawings, and is particularly and distinctly
pointed out and set forth in the appended claims.
[0027] FIG. 1 is a top rear perspective view of an axle/suspension
system incorporating a pair of prior art non-damping air springs,
and showing a pair of shock absorbers, with each one of the pair of
shock absorbers mounted on a respective one of the suspension
assemblies of the axle/suspension system;
[0028] FIG. 2 is a schematic cross-sectional view of the prior art
shock absorber shown in FIG. 1, showing the plunger extending into
the lower portion of the shock absorber and attached to a diaphragm
that includes a pair of openings and a blow off valve, and showing
the cylinder of the shock absorber filled with fluid;
[0029] FIG. 3 is a perspective view of a prior art air spring with
damping features, in section, showing the openings formed in the
piston top plate between and communicating with the piston chamber
and the bellows chamber, and also showing a bumper attached to the
top plate of the piston;
[0030] FIG. 4 is a graph showing the relative level of damping per
cycle over a critical range of frequencies of an axle/suspension
system incorporating the prior art non-damping air spring and shock
absorber shown in FIG. 1;
[0031] FIG. 5 is a graph showing the relative level of damping per
cycle over a critical range of frequencies of an axle/suspension
system incorporating the damping air spring shown in FIG. 3,
without using a shock absorber;
[0032] FIG. 6 is a perspective view of an axle/suspension system
incorporating a first preferred embodiment combination optimized
damping air spring and optimized shock absorber of the present
invention;
[0033] FIG. 7 is a schematic cross-sectional view of the optimized
shock absorber shown in FIG. 6, showing the plunger extending into
the lower portion of the shock absorber and attached to a diaphragm
that includes a pair of openings with the blow off valve
optimized;
[0034] FIG. 8 is a graph showing the relative level of damping per
cycle over a critical range of frequencies of the axle/suspension
incorporating the first preferred embodiment combination optimized
damping air spring and optimized shock absorber of the present
invention shown in FIG. 6;
[0035] FIG. 9 is a perspective view of an axle/suspension system
incorporating a second preferred embodiment combination optimized
damping air spring and traditional shock absorber of the present
invention;
[0036] FIG. 10 is a graph showing the relative level of damping per
cycle over a critical range of frequencies of the axle/suspension
system incorporating the second preferred embodiment combination
optimized damping air spring and traditional shock absorber of the
present invention shown in FIG. 8; and
[0037] FIG. 11 is a graph comparing the relative level of damping
per cycle over a critical range of frequencies of the
axle/suspension systems shown above in the graphs in FIGS. 4, 5, 8
and 10. Similar numerals refer to similar parts throughout the
drawings.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] In order to better understand the environment in which the
combination damping air spring and shock absorber for a heavy-duty
vehicle of the present invention is utilized, a trailing arm
overslung beam-type air-ride axle/suspension system that
incorporates a prior art non-damping air spring 24, is indicated
generally at 10, is shown in FIG. 1, and now will be described in
detail below.
[0039] It should be noted that axle/suspension system 10 is
typically mounted on a pair of longitudinally-extending
spaced-apart main members (not shown) of a heavy-duty vehicle,
which is generally representative of various types of frames used
for heavy-duty vehicles, including primary frames that do not
support a subframe and primary frames and/or floor structures that
do support a subframe. For primary frames and/or floor structures
that do support a subframe, the subframe can be non-movable or
movable, the latter being commonly referred to as a slider box.
Because axle/suspension system 10 generally includes an identical
pair of suspension assemblies 14, for sake of clarity and
conciseness only one of the suspension assemblies will be described
below.
[0040] Suspension assembly 14 is pivotally connected to a hanger 16
via a trailing arm overslung beam 18. More specifically, beam 18 is
formed having a generally upside-down integrally formed U-shape
with a pair of sidewalls 66 and a top plate 65, with the open
portion of the beam facing generally downwardly. A bottom plate
(not shown) extends between and is attached to the lowermost ends
of sidewalls 66 by any suitable means such as welding to complete
the structure of beam 18. Trailing arm overslung beam 18 includes a
front end 20 having a bushing assembly 22, which includes a
bushing, pivot bolts and washers as are well known in the art, to
facilitate pivotal connection of the beam to hanger 16. Beam 18
also includes a rear end 26, which is welded or otherwise rigidly
attached to a transversely extending axle 32.
[0041] Suspension assembly 14 also includes air spring 24, mounted
on and extending between beam rear end 26 and the main member (not
shown). Air spring 24 includes a bellows 41 and a piston 42. The
top portion of bellows 41 is sealingly engaged with a bellows top
plate 43. An air spring mounting plate 44 is mounted on top plate
43 by fasteners 45, which are also used to mount the top portion of
air spring 24 to the vehicle main member (not shown). Alternate
means for mounting top plate 43 to the vehicle main member, such as
direct attachment, via fasteners or welds, are also generally well
known in the art. Piston 42 is generally cylindrical-shaped and has
a generally flat bottom plate and top plate (not shown). The bottom
portion of bellows 41 is sealingly engaged with piston top plate
(not shown). The piston bottom plate rests on beam top plate 65 at
beam rear end 26 and is attached thereto in a manner well known to
those having skill in the art, such as by fasteners or bolts (not
shown). The piston top plate is formed without openings so that
there is no fluid communication between piston 42 and bellows 41.
As a result, piston 42 does not generally contribute any
appreciable volume to air spring 24. The top end of a shock
absorber 40 is mounted on an inboardly extending wing 17 of hanger
16 via a mounting bracket 19 and a fastener 15, in a manner well
known in the art. The bottom end of shock absorber 40 is mounted to
beam 18 (the mount not shown) in a manner well known to those
having skill in the art. For the sake of relative completeness, a
brake system 28 is shown mounted on prior art suspension assembly
14.
[0042] As mentioned above, axle/suspension system 10 is designed to
absorb forces that act on the vehicle as it is operating. More
particularly, it is desirable for axle/suspension system 10 to be
rigid or stiff in order to resist roll forces and thus provide roll
stability for the vehicle. This is typically accomplished by using
beam 18, which is rigid, and which also is rigidly attached to axle
32. It is also desirable, however, for axle/suspension system 10 to
be flexible to assist in cushioning the vehicle (not shown) from
vertical impacts and to provide compliance so that the
axle/suspension system resists failure. Such flexibility typically
is achieved through the pivotal connection of beam 18 to hanger 16
with bushing assembly 22. Air spring 24 cushions the ride of the
vehicle for cargo and passengers while shock absorber 40 assists in
controlling the ride of the vehicle.
[0043] Turning now to FIG. 2, prior art shock absorber 40 includes
an upper inverted cup portion 116 that is slip fit over cylinder
118. An eyelet 109 including a bushing assembly 108 is mounted on
the lowermost end of the shock absorber cylinder 118 and also on
the uppermost end of inverted cup portion 116. More specifically,
bushing assembly 108 includes an outer generally cylindrical
carrier 110 formed from metal or other sufficiently rigid material.
A bushing 112 formed with a continuous opening 113 at its center is
press fit into cylindrical carrier 110. An inner sleeve 114 having
a generally cylindrical shape and formed with a continuous opening
115 at its center is press fit into opening 113 of bushing 112.
Inner sleeve 114 extends generally outwardly past bushing 112 and
carrier 110. Carrier 110 is fixedly attached to the uppermost end
of a plunger 126, via welds or other similar means of rigid
attachment. Cylinder 118 includes a chamber 119, which is filled
with fluid 124. Chamber 119 also includes a generally circular flat
diaphragm 120 formed with a pair of openings 122 that allow
communication of fluid through the diaphragm and within or
throughout the entire chamber. The uppermost surface of diaphragm
120 is attached to plunger 126. Plunger 126 extends from diaphragm
120, through chamber 119 and fluid 124, through an opening 131
formed in the uppermost portion of cylinder 118, and is attached to
the inner surface of inverted cup 116 and carrier 110 as set forth
above. As inverted cup portion 116 slides downwardly over cylinder
118 of shock absorber 40 during operation of the vehicle, plunger
126 moves diaphragm 120 downwardly in direction D. Conversely, as
inverted cup portion 116 slides upwardly over lower portion 118 of
shock absorber 40 during operation of the vehicle, plunger 126
moves diaphragm 120 upwardly in direction U. The upward and
downward movement of diaphragm 120 provides viscous damping to
shock absorber 40 and in turn, the axle/suspension system to which
it is attached during operation of the heavy-duty vehicle. A blow
off valve 133 is located on diaphragm 120. Blow off valve 133
provides controlled relief of peak pressures on either side of
diaphragm 120 in the cylinder chamber 119 resulting from movement
of the diaphragm through fluid 124 contained in the cylinder
chamber. Blow off valve 133 is activated during high energy load
inputs, thereby reducing the pressure inside cylinder chamber 119
and reducing the rate of increase of damping within shock absorber
40. Conversely, blow off valve 133 typically remains closed for low
energy inputs.
[0044] Prior art air spring 24 described above, has very limited or
no damping capabilities because its structure, as described above,
does not provide for the same. Instead, prior art air spring 24
relies on shock absorber 40 to provide damping to axle/suspension
system 10.
[0045] Turning now to FIG. 4, the relative level of damping per
cycle of axle/suspension system 10, shown in FIG. 1, plotted over a
critical range of frequencies is shown. In this prior art
arrangement, shock absorber 40 is relied upon as the only means for
providing damping features to axle/suspension system 10. Because of
this, axle/suspension system 10 utilizing shock absorber 40 in
combination with a typical prior art air spring 24 without damping
features generally provides optimal damping at point A, at about
1.8 Hz. At higher frequencies, between about 12.0 Hz.-14.0 Hz at
point I, axle/suspension system 10 is subjected to increased
damping as a result of the continuously increasing damping curve of
typical prior art shock absorber 40. The increased damping of shock
absorber 40 causes increased transmissibility of the forces acting
on the axle/suspension system, which in turn can reduce the soft
ride characteristics of the axle/suspension system and can lead to
premature wear of the components of the axle/suspension system,
tires and other vehicle components. This increased damping
demonstrated by prior art shock absorber 40 of axle/suspension
system 10 can also potentially cause misting of the shock absorber
when it encounters high energy inputs as described previously,
which can adversely affect components surrounding the shock
absorber by contaminating them with fluid from the shock absorber
and can also result in premature replacement of the shock absorbers
or surrounding components. In addition, the increased damping of
prior art shock absorber 40 requires large and heavy mounts for
effective transmission of the forces acting on the shock absorber
through the axle/suspension system during operation of the vehicle,
which undesirably increase weight of the vehicle, and in turn
increases cost to operate the vehicle due to increased fuel
consumption.
[0046] A prior art air spring with damping features is shown
generally at 224 in FIG. 3, is used in conjunction with an axle of
an axle/suspension system having a gross axle weight rating (GAWK)
of about 20,000 lbs., is the subject of U.S. Pat. No. 8,540,222 and
will be described in detail below. Like prior art air spring 24
described above, air spring 224 is also incorporated into
axle/suspension system 10, or other similar air-ride
axle/suspension system. However, air spring 224 is typically
utilized without shock absorber 40. Air spring 224 includes a
bellows 241 and a piston 242. The top end of bellows 241 is
sealingly engaged with a bellows top plate 243 in a manner well
known in the art. An air spring mounting plate (not shown) is
mounted on the top surface of top plate 243 by fasteners (not
shown) which are also used to mount the top portion of air spring
224 to a respective one of the main members (not shown) of the
vehicle. Alternatively, bellows top plate 243 could also be mounted
directly on a respective one of the main members (not shown) of the
vehicle. Piston 242 is generally cylindrical-shaped and includes a
continuous generally stepped sidewall 244 attached to a generally
flat bottom plate 250 and integrally formed with a top plate 282.
Bottom plate 250 is formed with an upwardly-extending central hub
252. Central hub 252 includes a bottom plate 254 formed with a
central opening 253. A fastener 251 is disposed through opening 253
in order to attach piston 242 to beam top plate 65 at beam rear end
26 (FIG. 1).
[0047] Top plate 282, sidewall 244 and bottom plate 250 of piston
242 define a piston chamber 299 having an interior volume V.sub.1.
Top plate 282 of piston 242 is formed with a circular
upwardly-extending protrusion 283 having a lip 280 around its
circumference. Lip 280 cooperates with the lowermost end of bellows
241 to form an airtight seal between the bellows and the lip, as is
well known to those of ordinary skill in the art. Bellows 241, top
plate 243 and piston top plate 282 define a bellows chamber 298
having an interior volume V.sub.2 at standard static ride height. A
bumper 281 is rigidly attached to a bumper mounting plate 286 by
means generally well known in the art. Bumper mounting plate 286 is
in turn mounted on piston top plate 282 by a fastener 284. Bumper
281 extends upwardly from the top surface of bumper mounting plate
286. Bumper 281 serves as a cushion between piston top plate 282
and bellows top plate 243 in order to keep the plates from
contacting one another during operation of the vehicle, which can
potentially cause damage to the plates.
[0048] Bellows chamber 298 preferably has interior volume V.sub.2
at standard static ride height of from about 305 in..sup.3 to about
915 in..sup.3. Piston chamber 299 preferably has interior volume
V.sub.1 at standard static ride height of from about 150 in..sup.3
to about 550 in..sup.3.
[0049] Piston top plate 282 is formed with a pair of openings 285,
which allow volume V.sub.1 of piston chamber 299 and volume V.sub.2
of bellows chamber 298 to communicate with one another. More
particularly, openings 285 allow fluid or air to pass between
piston chamber 299 and bellows chamber 298 during operation of the
vehicle. Piston top plate openings 285 preferably have a combined
cross-sectional area of from about 0.039 in.sup.2 to about 0.13
in.sup.2.
[0050] The ratio of the cross-sectional area of openings 285
measured in in..sup.2 to the volume of piston chamber 299 measured
in in..sup.3 to the volume of bellows chamber 298 measured in
in..sup.3 is in the range of ratios of from about 1:600:1200 to
about 1:14100:23500.
[0051] Having now described the structure of prior art damping air
spring 224, the operation of the damping characteristics of the air
spring will be described in detail below. When axle 32 of
axle/suspension system 10 experiences a jounce event, such as when
the vehicle wheels encounter a curb or a raised bump in the road,
the axle moves vertically upwardly toward the vehicle chassis. In
such a jounce event, bellows chamber 298 is compressed by
axle/suspension system 10 as the wheels of the vehicle travel over
the curb or the raised bump in the road. The compression of air
spring bellows chamber 298 causes the internal pressure of the
bellows chamber to increase. Therefore, a pressure differential is
created between bellows chamber 298 and piston chamber 299. This
pressure differential causes air to flow from bellows chamber 298,
through piston top plate openings 285 and into piston chamber 299.
The restricted flow of air between bellows chamber 298 into piston
chamber 299 through piston top plate openings 285 causes damping to
occur. As an additional result of the airflow through openings 285,
the pressure differential between bellows chamber 298 and piston
chamber 299 is reduced. Air continues to flow through piston top
plate openings 285 until the pressures of piston chamber 299 and
bellows chamber 298 have equalized.
[0052] Conversely, when axle 32 of axle/suspension system 10
experiences a rebound event, such as when the vehicle wheels
encounter a large hole or depression in the road, the axle moves
vertically downwardly away from the vehicle chassis. In such a
rebound event, bellows chamber 298 is expanded by axle/suspension
system 10 as the wheels of the vehicle travel into the hole or
depression in the road. The expansion of air spring bellows chamber
298 causes the internal pressure of the bellows chamber to
decrease. As a result, a pressure differential is created between
bellows chamber 298 and piston chamber 299. This pressure
differential causes air to flow from piston chamber 299, through
piston top plate openings 285, and into bellows chamber 298. The
restricted flow of air through piston top plate openings 285 causes
damping to occur. As an additional result of the airflow through
openings 285, the pressure differential between bellows chamber 298
and piston chamber 299 is reduced. Air will continue to flow
through the piston top plate openings 285 until the pressures of
piston chamber 299 and bellows chamber 298 have equalized. When
little or no suspension movement has occurred over a period of
several seconds the pressure of bellows chamber 298 and piston
chamber 299 can be considered equal.
[0053] By adjusting the relative sizes of volume V.sub.1 of piston
chamber 299, volume V.sub.2 of bellows chamber 298, and/or piston
top plate openings 285, it is possible to tune the level of damping
that is achieved as well as the frequency at which the highest
level of damping occurs. The level of damping achieved is measured
by the energy that is lost through damping over one cycle or
oscillation. For example, a relatively smaller bellows chamber
volume V.sub.2, will generally produce a higher level of damping,
as the pressure change within bellows chamber 298 will be higher
for a given event, i.e., a higher pressure differential means more
flow through piston top plate openings 285, thereby resulting in
more damping. By further example, a relatively larger piston
chamber volume V.sub.1, will also generally produce a higher level
of damping, as the pressure differential between piston chamber 299
and bellows chamber 298 will generally take longer to equalize,
i.e., more air will need to flow through piston top plate openings
285 resulting in more damping between the piston chamber and the
bellows chamber. By further example, changing the relative
cross-sectional size, shape, number or even the length of piston
top plate openings 285, will in turn affect the time it takes for
the pressures in piston chamber 299 and bellows chamber 298 to
equalize. Therefore, the cross-sectional size of piston top plate
openings 285 can be altered to both vary the level of damping and
the frequency at which the highest level of damping occurs.
[0054] Turning now to FIG. 5, the relative level of damping per
cycle over a critical range of frequencies of axle/suspension
system 10 incorporating prior art damping air spring 224 without
shock absorber 40 is shown. As can be seen in FIG. 5, the
combination of axle/suspension system 10 with damping air spring
224 without shock absorber 40 shows maximum damping at B around the
1.5-4.0 Hz range. As the frequency of the inputs on axle/suspension
system 10 increases, the relative damping provided by damping air
spring 224 begins to decline as shown at C. This is because damping
air spring 224 provides less damping at frequencies above about 6.0
Hz. Such reduced damping at higher frequencies can potentially
cause tire wear and payload damage.
[0055] More specifically, prior art air springs 224 with damping
features may potentially provide less than optimal damping at
critical higher frequencies D, such as about 13.0 Hz, which can in
turn potentially cause reduced life of the components of the
axle/suspension system, including potentially increased tire wear
and payload damage.
[0056] Prior art shock absorbers 40, such as those of the type
shown in FIGS. 1 and 2 have a continuously increasing damping curve
at higher critical frequencies I, around about 13.0 Hz.
[0057] This means that as the frequency of the inputs on
axle/suspension system 10 increase, the damping provided by shock
absorber 40 to the axle/suspension system is increased. This
increased damping of shock absorber 40 at higher input frequencies
causes increased transmissibility of the forces acting on
axle/suspension system 10, which in turn can reduce the soft ride
characteristics of the axle/suspension system at higher frequencies
and can also lead to premature wear and reduced life of the
components of the axle/suspension system, tires and other
components of the vehicle. Because prior art shock absorber 40
exhibits a continuously increasing damping curve, when the shock
absorber encounters high energy inputs, "misting" of the shock
absorber as described above can occur which can result in the
potential need for premature replacement of the shock absorbers or
other components and may potentially cause contamination of
surrounding components. The combination damping air spring and
shock absorber of the present invention, overcomes these problems
and the advantages and benefits of the invention will be described
in detail below.
[0058] A first preferred embodiment combination damping air spring
and shock absorber 300 is shown generally in FIGS. 6 and 7 and will
be described in detail below. Damping air spring 324 is generally
identical to prior art air spring 224 with damping features
described in detail above, and its placement on axle/suspension
system 10 is also generally identical. Optimized shock absorber 340
is similar in some respects to prior art shock absorber 40
described in detail above, in that the placement of shock absorber
340 on axle/suspension system 10 is generally identical to the
placement of prior art shock absorber 40 described in detail above.
However, optimized shock absorber 340 is smaller and less costly to
manufacture than prior art shock absorber 40 and utilizes mounting
hardware having a reduced size, thus saving weight.
[0059] Turning now to FIG. 7, optimized shock absorber 340 is shown
removed from axle/suspension system 10. Optimized shock absorber
340 includes an upper inverted cup portion 316 that is slip fit
over a cylinder 318. An eyelet 309 including a bushing assembly 308
is mounted on the lowermost end of the shock absorber cylinder 318
and also on the uppermost end of inverted cup portion 316. More
specifically, bushing assembly 308 includes an outer generally
cylindrical carrier 310 formed from metal or other sufficiently
rigid material. A bushing 312 formed with a continuous opening 313
at its center is press fit into cylindrical carrier 310. An inner
sleeve 314 having a generally cylindrical shape and formed with a
continuous opening 315 at its center is press fit into opening 313
of bushing 312. Inner sleeve 314 extends generally outwardly past
bushing 312 and carrier 310. Carrier 310 is fixedly attached to the
uppermost end of a plunger 326 via welds or other similar means of
rigid attachment. Cylinder 318 includes a chamber 319, which is
filled with fluid 325. Chamber 319 also includes a generally
circular flat diaphragm 320 formed with a pair of openings 322 that
allow communication of fluid through the diaphragm and within or
throughout the entire chamber. The uppermost surface of diaphragm
320 is attached to plunger 326. Plunger 326 extends from diaphragm
320, through chamber 319 and fluid 325, through an opening 331
formed in the uppermost portion of cylinder 318, and is attached to
inverted cup 316 and carrier 310. As inverted cup portion 316
slides downwardly over cylinder 318 of optimized shock absorber 340
during operation of the vehicle, plunger 326 moves diaphragm 320
downwardly in direction D. Conversely, as inverted cup portion 316
slides upwardly over lower portion 318 of optimized shock absorber
340 during operation of the vehicle, plunger 326 moves diaphragm
320 upwardly in direction U. The upward and downward movement of
diaphragm 320 through fluid 325 provides viscous damping to shock
absorber 340 and in turn the axle/suspension system to which it is
attached during operation of the heavy-duty vehicle.
[0060] The primary difference between optimized shock absorber 340
of the present invention and prior art shock absorber 40 is that
the optimized shock absorber includes an optimized blow off valve
333 and as a result generates reduced damping across all
frequencies. In addition, the mount of eyelet 309 to the uppermost
end of inverted cup portion 316 and the lowermost portion of shock
absorber cylinder 318 is less robust, which saves weight. The less
robust mount is sufficient because of the reduced damping required
by the shock absorber because it is being used in combination with
damping air spring 324.
[0061] Turning now to FIG. 8, the relative level of damping per
cycle over a critical range of frequencies of an axle/suspension
system incorporating first preferred embodiment combination damping
air spring and shock absorber 300 of the present invention is
shown. As can be seen in FIG. 8, combination damping air spring and
shock absorber 300 of the present invention provides optimal
damping to the axle/suspension system throughout the entire range
of critical natural frequencies of the axle/suspension system from
about 1.8 Hz E to about 13.0 Hz F, and also across the entire range
of frequencies, mainly from about 0.0 Hz to about 14.0 Hz. More
specifically, damping air spring 324 primarily provides optimal
damping to axle/suspension system 10 at lower frequencies below
about 6 Hz, while optimized shock absorber 340 primarily provides
optimal damping to the axle/suspension system at higher frequencies
above about 6 Hz. Combination damping air spring and shock absorber
300 of the present invention provides optimal damping across the
entire range of frequencies including all critical ranges of
frequencies that include body bounce mode, 1.8 Hz, and wheel hop
mode, 13.0 Hz for a trailer.
[0062] Combination damping air spring and shock absorber 300 of the
present invention, overcomes the problems associated with prior art
damping air springs 224 and prior art shock absorbers 40 utilized
with non-damping air springs 24, by providing damping air spring
324 that is utilized in combination with optimized shock absorber
340 resulting in optimized damping characteristics for
axle/suspension system 10 across the entire spectrum of critical
input frequencies. Combination damping air spring and shock
absorber 300 for heavy-duty vehicles of the present invention
allows tuning of certain structural components of shock absorber
340 to provide optimal damping at higher frequencies, resulting in
improved damping to axle/suspension system 10 while reducing
transmissibility and misting that are common in prior art standard
shock absorbers 40, potentially saving weight and cost, and
allowing the heavy-duty vehicle to haul more cargo. Moreover,
reducing transmissibility of road inputs into the components of
axle/suspension system 10 during operation of the vehicle increases
the durability of the axle/suspension system and the components of
the axle/suspension system while maintaining soft ride
characteristics of the axle/suspension system at higher critical
input frequencies.
[0063] Turning now to FIG. 9, a second preferred embodiment
combination damping air spring and shock absorber 400 is shown
generally in FIG. 9 and will be described in detail below. Damping
air spring 424 is generally identical to prior art air spring 224
with the damping features described in detail above, and its
placement on axle/suspension system 10 is also generally identical.
Shock absorber 440 is generally identical to prior art shock
absorber 40 described in detail above, and placement of shock
absorber 440 on axle/suspension system 10 is also generally
identical to the placement of prior art shock absorber 40 described
in detail above.
[0064] In recent years, certain jurisdictions have implemented
"road friendly" legislation. In those jurisdictions, government
regulations require extremely high levels of damping for vehicles
traveling on roads within the jurisdiction. Typically, this
increased damping has been accomplished by using shock absorbers
that are "extra-duty" and that provide the required minimum
threshold of damping. These shock absorbers require heavy/robust
mounting structures which are costly.
[0065] Second preferred embodiment combination damping air spring
and shock absorber 400 of the present invention accomplishes the
increased levels of damping through the utilization of a
combination of a damping air spring 424 and a shock absorber
440.
[0066] Turning now to FIG. 10, the relative level of damping per
cycle over a critical range of frequencies of an axle/suspension
system incorporating second preferred embodiment combination
damping air spring and shock absorber 400 of the present invention
is shown. As can be seen by FIG. 10, combination damping air spring
and shock absorber 400 of the present invention provides increased
levels of damping to the axle/suspension system at both critical
natural frequencies of the axle/suspension system, 1.8 Hz G and
13.0 Hz H. Such increased damping allows second preferred
embodiment combination damping air spring and shock absorber 400 of
the present invention to provide damping that is compliant with
"road friendly" jurisdictions, without the need for implementing
"extra-duty" shock absorbers that are heavy and that require
heavy/robust mounting structures. Thus, utilization of second
preferred embodiment combination damping air spring and shock
absorber 400 of the present invention saves weight which in turn
allows vehicles utilizing the invention to carry more cargo.
[0067] Turning now to FIG. 11, the relative level of damping per
cycle over a critical range of frequencies of the various
axle/suspension systems shown in the graphs in FIGS. 4, 5, 8 and 10
are shown in comparison with one another.
[0068] It is contemplated that first and second preferred
embodiment combination damping air spring and shock absorber
300,400 of the present invention could be utilized on
tractor-trailers or other heavy-duty vehicles, including trucks,
specifically class-8 commercial trucks, or buses and the like
having one or more than one axle, without changing the overall
concept or operation of the present invention. It is further
contemplated that preferred embodiment combination damping air
spring and shock absorber 300,400 of the present invention could be
utilized on vehicles having frames or subframes which are moveable
or non-movable without changing the overall concept of the present
invention. It is yet even further contemplated that preferred
embodiment combination damping air spring and shock absorber
300,400 of the present invention could be utilized on all types of
air-ride leading and/or trailing arm beam-type axle/suspension
system designs known to those skilled in the art without changing
the overall concept or operation of the present invention. For
example, the present invention finds application in beams or arms
that are made of materials other than steel, such as aluminum,
other metals, metal alloys, composites, and/or combinations
thereof. It is also contemplated that preferred embodiment
combination damping air spring and shock absorber 300,400 of the
present invention could be utilized on axle/suspension systems
having either an overslung/top-mount configuration or an
underslung/bottom-mount configuration, without changing the overall
concept of the present invention. The present invention also finds
application in beams or arms with different designs and/or
configurations than that shown above, such as solid beams,
shell-type beams, truss structures, intersecting plates, spring
beams and parallel plates. The present invention also finds
application in intermediary structures such as spring seats. It is
also contemplated that preferred embodiment combination damping air
spring and shock absorber 300,400 of the present invention could be
utilized in conjunction with other types of air-ride rigid
beam-type axle/suspension systems such as those using U-bolts,
U-bolt brackets/axle seats and the like, without changing the
overall concept or operation of the present invention. It is also
contemplated that preferred embodiment combination damping air
spring and shock absorber 300,400 of the present invention could be
formed from various materials, including but not limited to
composites, metal and the like, without changing the overall
concept or operation of the present invention. It is also
contemplated that preferred embodiment combination damping air
spring and shock absorber 300,400 of the present invention could be
utilized with any fluid, such as air or hydraulic fluid, without
changing the overall concept of the present invention. It should
also be understood that preferred embodiment combination damping
air spring and shock absorber 300,400 of the present invention
could be modified to be utilized on busses where the critical body
bounce mode is 1.5 Hz and wheel hop mode is 11.0 Hz without
changing the overall concept or operation of the present invention.
It is even further contemplated that damping air springs 324,424
utilized in preferred embodiment combination damping air spring and
shock absorber 300,400, respectively, could be connected via
conduit(s) to an external reservoir instead of the reservoir
contained in piston chamber 299, without changing the overall
concept or operation of the present invention. It should also be
understood that different types of axle/suspension systems may
exhibit different critical natural frequencies for body bounce mode
and wheel hop mode and the teachings herein are applicable thereto.
It is contemplated that preferred embodiment combination damping
air spring and shock absorber 300 of the present invention could be
utilized with a shock absorber that does not include a blow off
valve, without changing the overall concept or operation of the
present invention. It is also contemplated that damping air springs
324,424 utilized in preferred embodiment combination damping air
spring and shock absorber 300,400, respectively, could be different
types of damping air springs having different structures and
make-ups, without changing the overall concept or operation of the
present invention.
[0069] Accordingly, the damping air spring and shock absorber
combination for heavy-duty vehicle axle/suspension systems is
simplified, provides an effective, safe, inexpensive and efficient
structure and method which achieves all the enumerated objectives,
provides for eliminating difficulties encountered with prior art
air springs and shock absorbers, and solves problems and obtains
new results in the art.
[0070] In the foregoing description, certain terms have been used
for brevity, clearness and understanding; but no unnecessary
limitations are to be implied therefrom beyond the requirements of
the prior art, because such terms are used for descriptive purposes
and are intended to be broadly construed.
[0071] Moreover, the description and illustration of the invention
is by way of example, and the scope of the invention is not limited
to the exact details shown or described.
[0072] Having now described the features, discoveries and
principles of the invention, the manner in which the damping air
spring and shock absorber combination for heavy-duty vehicle
axle/suspension systems is used and installed, the characteristics
of the construction, arrangement and method steps, and the
advantageous, new and useful results obtained; the new and useful
structures, devices, elements, arrangements, process, parts and
combinations are set forth in the appended claims.
* * * * *